Mitochondria are organelles inside our cells that are essential for generating metabolic energy in the form of ATP. It is thought that these organelles originally came from aerobic bacteria that were ingested by the first eukaryotic cells. In fact, mitochondria have their very own DNA. Cells that have higher energy needs, like those in the brain and heart, contain more mitochondria.
When cells die, mitochondrial DNA can end up in the circulation where it is associated with a variety of inflammatory diseases including cardiovascular disease, atherosclerosis, cancer, and autoimmune diseases.
Interestingly, mitochondrial DNA is naturally often found in the circulation during pregnancy. Pregnancy also activates the immune system and is considered an inflammatory state that helps protect the mother as well as the developing fetus. As the placenta grows, cells that make up the placenta turnover resulting in the death (apoptosis) of some cells and the generation of new cells. The dying cells can release fetal DNA into the mother’s circulation, which is seen in humans as well as primates and rodents.
Damage to the placenta or maternal organs and even bacterial infections can increase the amount of circulating mitochondrial DNA, which is thought to contribute to complications in pregnancy. Women with preeclampsia, for example, have higher inflammation and circulating mitochondrial DNA. For this reason, elevated levels of circulating mitochondrial DNA are thought to be an early indicator of pregnancy complications. In turn, mitochondrial DNA in healthy pregnancies is thought to be involved in communication between the fetus and mother and may be involved in signaling childbirth as levels also normally increase with advancing pregnancy.
JL Bradshaw, SC Cushen, NR Phillips, S Goulopoulou. Circulating cell-free mitochondrial DNA in pregnancy. Physiology. 37(4): 0, 2022.
Categories: Reproduction and Development